1. Field of the Invention
The present invention relates to a digital data processing system and, more particularly, to a multiprocess digital data processing system in which information, including operands and instructions, can be organized as object-based information which is addressed by addresses containing object, offset and length fields and which includes protection means for preventing unauthorized access by a user to objects of another user.
2. Description of Prior Art
A general trend in the development of data processing systems has been towards systems suitable for use in interconnected data processing networks. Another trend has been towards data processing systems wherein the internal structure of the system is flexible, protected from users, and effectively invisible to the user and wherein the user is presented with a flexible and simplified interface to the system.
Certain problems and shortcomings affecting the realization of such a data processing system have appeared repeatedly in the prior art and must be overcome to create a data processing system having the above attributes. These prior art problems and limitations include the following topics.
First, the data processing systems of the prior art have not provided a system wide addressing system suitable for use in common by a large number of data processing systems interconnected into a network. Addressing systems of the prior art have not provided sufficiently large address spaces and have not allowed information to be permanently and uniquely identified. Prior addressing systems have not made provisions for information to be located and identified as to type or format, and have not provided sufficient granularity. In addition, prior addressing systems have reflected the physical structure of particular data processing systems. That is, the addressing systems have been dependent upon whether a particular computer was, for example, an 8, 16, 32, 64 or 128 bit machine. Since prior data processing systems have incorporated addressing mechanisms wherein the actual physical structure of the processing system is apparent to the user, the operations a user could perform have been limited by the addressing mechanisms. In addition, prior processor systems have operated as fixed word length machines, further limiting user operations.
Prior data processing systems have not provided effective protection mechanisms preventing one user from effecting another user's data and programs without permission. Such protection mechanisms have not allowed unique, positive identification of users requesting access to information, or of information, nor have such mechanisms been sufficiently flexible in operation. In addition, access rights have pertained to the users rather than to the information, so that control of access rights has been difficult. Finally, prior art protection mechanisms have allowed the use of "Trojan Horse arguments". That is, users not having access rights to certain information have been able to gain access to that information through another user or procedure having such access rights.
Yet another problem of the prior art is that of providing a simple and flexible interface user interface to a data processing system. The character of user's interface to a data processing system is determined, in part, by the means by which a user refers to and identifies operands and procedures of the user's programs and by the instruction structure of the system. Operands and procedures are customarily referred to and identified by some form of logical address having points of reference, and validity, only within a user's program. These addresses must be translated into logical and physical addresses within a data proccessing system each time a program is executed, and must then be frequently retranslated or generated during execution of a program. In addition, a user must provide specific instructions as to data format and handling. As such reference to operands or procedures typically comprise a major portion of the instruction stream of the user's program and requires numerous machine translations and operations to implement. A user's interface to a conventional system is thereby complicated, and the speed of execution of programs reduced, because of the complexity of the program references to operands and procedures.
A data processing system's instruction structure includes both the instructions for controlling system operations and the means by which these instructions are executed. Conventional data processing systems are designed to efficiently execute instructions in one or two user languages, for example, FORTRAN or COBOL. Programs written in any other language are not efficiently executable. In addition, a user is often faced with difficult programming problems when using any high level language other than the particular one or two languages that a particular conventional system is designed to utilize.
Yet another problem in conventional data processing systems is that of protecting the system's internal mechanisms, for example, stack mechanisms and internal control mechanisms, from accidental or malicious interference by a user.
Finally, the internal structure and operation of prior art data processing systems have not been flexible, or adaptive, in structure and operation. That is, the internal structure structure and operation of prior systems have not allowed the systems to be easily modified or adapted to meet particular data processing requirements. Such modifications may include changes in internal memory capacity, such as the addition or deletion of special purpose subsystems, for example, floating point or array processors. In addition, such modifications have significantly effected the users interface with the system. Ideally, the actual physical structure and operation of the data processing system should not be apparent at the user interface.
The present invention provides data processing system improvements and features which solve the above-described problems and limitations.
The digital computer system of the present invention includes a memory system comprising mass storage devices and one or more processors connected to the memory system. The memory system is organized into objects containing data items, e.g., operands and instructions, each object being identified by an object identifier. Locations of data items in the memory system are specified by means of the object identifier for the object containing the data item. Objects are addressed by addresses containing object fields, offset fields and length fields for specifying the location and number of bits in an accessed object. General register files are divided into vertically ordered registers having parallel-operating and addressed parts for storing the object, offset and length fields.
Access to the data items in objects is controlled by protection mechanisms of the system. When the digital computer system processes data in an object, it does so for a subject representing an entity using the computer system. An access control list associated with each object defines sets of subjects in a set of memory operations which a subject in a given set of subjects may perform on data items in the object. A memory operation on a data item in an object succeeds only if there is an access control list entry associated with the object which allows the subject for whom the processor is performing the memory operation to perform that operation on the data in the object.
It is thus an object of the present invention to provide an improved data processing system.
It is another object of the present invention to provide a data processing system capable of use in large, interconnected data processing networks.
It is yet another object of the present invention to provide an improved addressing mechanism suitable for use in large, interconnected data processing networks.
It is a further object of the present invention to provide an improved information protection mechanism.
It is still another object of the present invention to provide a simplified and flexible user interface to a data processing system.
It is yet a further object of the present invention to provide an improved mechanism for referring to operands.
It is a still further object of the present invention to provide an instruction structure allowing efficient data processing system operation with a plurality of high level user languages.
It is a further object of the present invention to provide data processing internal mechanisms protected from user interference.
It is yet another object of the present invention to provide a data processing system having a flexible internal structure capable of multiple, concurrent operations.
Other objects, advantages and features of the present invention will be understood by those of ordinary skill in the art, after referring to the following detailed description of the preferred embodiments and drawings wherein: